The rest of the England squad have since all undergone lateral flow and PCR tests, which have come back negative.
It means the squad can press on with preparations for Saturday’s Test against Australia at Twickenham.
When Marler tested positive for Covid-19 on Monday, the England squad all returned to their rooms as a precaution before taking lateral flow tests.
After they came back negative, the squad trained yesterday but underwent a further round of PCR tests to ensure there was no outbreak in camp.
England’s Autumn Nations Series campaign has been disrupted by Covid-19 already, with a member of the support staff testing positive last week.
Captain Owen Farrell also tested positive ahead of last’s week match with Tonga, forcing him to sit out the 69-3 win.
That test, however, has since been confirmed as a false positive and Farrell is set to return this Saturday against Australia.